Cyclic O,O,S-triesters of phosphorodithioic acid

ABSTRACT

Cyclic O,O,S - Triesters of phosphorodithioic acid are excellent accelerators of sulfur vulcanization at elevated temperatures, thereby making possible a considerable reduction in the cure time. Additionally, certain novel compounds of the above class and their preparation are disclosed.

United States Patent Nudenberg et al.

CYCLIC 0.0.S-TRIESTERS OF PHOSPHORODITIIIOIC ACID inventors: Walter Nudenberg, Newtown,

Conn.; Merlin P. Harvey, Denison, Iowa; James Urquhart Mann,

Wayne, NJ.

Assignee: Uniroyal, Inc., New York, NY.

Filed: July 17, 1974 Appl. No.: 489,295

Related U.S. Application Data Division of Ser. No. 282,640, Aug. 2l, 1972, which is a division of Ser. No. 66,870, Aug. 25, 1970, Pat. No. 3,712,878.

US. Cl 260/934; 260/937 Int. Cl C07d 105/04 [451 July 29, 1975 [58] Field of Search 260/934, 937

[56] References Cited UNITED STATES PATENTS 3,159,664 l2/l964 Bartlett 260/937 Primary ExaminerAnton H. Sutto Attorney, Agent, or Firm-Robert J. Patterson, Esq.

[57] ABSTRACT 3 Claims, No Drawings CYCLIC 0,0,S-TRIESTERS F wherein R and R are alkyl groups which can be the PHOSPHORODITHIOIC ACID same or different andeach group can havejrom l to 5 carbon'atoms, and wherein x is 1 or 2, (0) portion figgfgiggg represents the optional presence of an oxygen atom, 5 and R is the after-addition moiety of the reactant to This application is a division of our copending appliwhich DTP has been added. The .R moiety can be alkyl cation Ser. No. 282,640, filed Aug. 21, 1972 which in except methyl, alkenyl, alkynyl, aralkyl except benzyl turn is a division of our copending application Ser. No. and alkyl-substituted aralkyl except alkyl substituted 66,870, filed Aug. 25, 1970, issued on Jan. 23, 1973 as benzyl, an alicyclic radical (including polycyclic radi- U.S. Pat. No. 3,712,878. cals) and the alkyl substituted derivatives thereof, and

This invention relates to (1) the use of 0,0,S- a heterocyclic radical containing one or more heteroattriesters of phosphorodithioic acid to accelerate the oms selected from sulfur, oxygen and nitrogen. R can sulfur vulcanization of rubbery elastomers at elevated also be temperatures (i.e., at approximately 400F and higher), (2) vulcanizable compositions containing such triests 0 CH 3 ers, (3) improved cured vulcanizates produced: in ack! 3 cordance with the foregoing use and (4) many of the S C triesters themselves as novel compounds. O CH R The 0,0,S-triesters of phosphorodithioic acid that 2 4 are within the invention are the addition products, or adducts, resulting from the addition of cyclic 0,0-2,2- dimethyltrimethylene phosphorodithioic acid (hereinto give bis-diesters which are made by reacting two aft r referred to as DTP COYlVmliflme)v hOmO- moles of DTP or its homologues with alcoholic iodine, logues across an unsaturated bond, such as, for examin which case the optional oxygen is not present. R and pic, R may have the same values as R, and R Addition- 0 L\ as in styrene or alkene;

-CC as in pnenylace'cylene or acetylene;

H C@ as in benzalazine; and

-C .=N as in acetonitrile.

The compound to which DTP or its homologues add ally, the R moiety can contain any of the following can have more than one unsaturated bond, and the adfunctional substituent groups: ditive reaction may occur at one or more of such bonds C=N The structural formula of DTP is: i

; -CH. OH R /CH2-O\ C NH N/ -CH(OH)- 2 a CH -0 SH l Accordingly, the generalized structure of the adduct :CWOH can be represented as follows: g

R CH -O S -C-N 1\ 2 H -1 11 ca -o sa 0..

-C-NHNH -c-si ll N g O O I- N- c-o- 5 e L I -O- O fi..g N-|C'-S- s I -I S -S- N C-N When R is an aliphatic compound or contains an ali- O -SS- a v phatic moiety (for instance, when R is an alkyl or an alkyl substituted alicyclic radical), such aliphatic compound or moiety can have from 1 to 10 carbon atoms,

\ preferably from 1 'to 5. Examples of R radicals contain- -Cl ing both nonfunctional and functional moieties follow. Examples of R'as a monovalent radical (i.e., x=l) are:

gL-hydroxyphe ne thyl l-- (dodecyloxycarbonyl' )echyl (3) -CH CH COOC H & (benzylidenehydrazino )benzyl 1 2, 3a, l, 7, 7a-hexahydro-Q, 7-methanoinden-l-yl 1', 2, 3a, l, 7, Ya-hexahydro l 7-me thanoinden-Z-yl (7) -CH -CH-(CH -CH 1 -me thylheptyl CH )3 3 -CH2 HCH=CH- 3-mechyl-l-bucenylene ethylenecarboxyethylene -CH CH GH -CH p-phenylenediethylene 2-methyltetramethylene 2-3-dimethyltetra.methylene ethyl eneearbonyliminotrimethylene oxybis (trimethylene) CH CH, l 3 5 2 5-dimethylhexamethylene Additional representative examples of R are ethyl, propyl, butyl, pentyl, vinyl, allyl, isopropenyl, butenyl, pentenyl, butynyl, pentynyl, phenethyl, phenylpropyl, phenylbutyl, phenylpentyl, naphthylmethyl, naphthylethyl, naphthylpropyl, naphthylbutyl, naphthylpentyl, cyclopropyl, cyclobutyl, cyclopentyl, cyclohexyl, decahydronaphthyl.

Representative examples of heterocyclic radicals containing one or more heteroatoms selected from sulfur, oxygen and nitrogen and dihydrothienyl, tetrahydrothienyl, 2,3-dihydrobenzothienyl, dihydrofuryl, dihydropyranyl, chromanyl, pyrrolinyl, piperidyl, indolinyl, indolidinyl, l,3dithiolanyl, 1,4-dioxanyl, imidazolinyl, imidazolidinyl, pyrazolidinyl, pyrazolinyl, dihydropyrazinyl, piperazinyl, dihydropyrimidinyl, dihydropyridazinyl, benzimidazolinyl, 1,2-dihydrobenzotriazolyl, dihydroquinolyl, 1,2-dihydroquinoxalinyl, dihydrooxathiinyl, thiazolinyl, isothiazolidinyl, dihydrobenzothiazolyl, oxazolidinyl, isoxazolidinyl, oxazolinyl, isoxazolinyl, dihydrooxazinyl, Z-benzoxazolinyl, oxadiazolidinyl, oxathiazolinyl.

Representative examples of alkyl substituted homologues of the aforementioned radicals are methylpropyl, methylbutyl, methylpentyl, ethylpropyl, ethylbutyl, ethylpentyl, 1,1 ,3,3-tetramethylbutyl, 4,4- dimethylhexyl, methylbutenyl, methylpentenyl, methylbutynyl, methylpentynyl, a-methylbenzyl, a-ethylbenzyl, a-propylbenzyl, a-butylbenzyl, methylphenethyl, ethylphenethyl, propylphenethyl, butylphenethyl, a-methylnaphthylmethyl, ethylnaphthylpropyl propylnaphthylbutyl, methylcyclohexyl, ethylcyclopropyl, propylcyclobutyl, methylphenycyclohexyl, ethyltetrahydronaphthyl, butyltetrahydronaphthyl.

Representative examples of alkyl substituted heterocyclic radicals are phenethyldihydrothienyl, methylbenzodihydrothienyl, propyldihydrofuryl, butyldihydropyranyl, isopropylchromanyl, butylpyrroinyl, ethylpiperidyl, ethylindolinyl, isopropylindolinyl, methyl-1,3-dithiolanyl, ethyltetrahydrothienyl, propyl- 1,4-dithianyl, butyl-l ,3-dioxolanyl, methyl-1,4- dioxanyl, ethylimidazolinyl, propylimidazolidinyl, butylpyrazolidinyl, pentylpyrazolinyl, methylpiperazinyl, ethyldihydropyrimidinyl, propyldihydropyridazinyl, methyl-2,3-dihydrobenzimidazolyl, ethyltetrahydroquinolyl, propyltetrahydroquinolyl, propyldihydroquinoxalinyl, methyldihydrooxathiinyl, ethylthiazolinyl, propylisothiazolinyl, methyldihydrobenzothiazolyl, butyloxazolidinyl, pentylisoxazolidinyl, methyloxazolinyl, ethylisoxazolinyl, propyldihydrooxazinyl, methyldihydrobenzoxazolyl, propyloxadiazolinyl, butyloxathiazolinyl.

Of the 0,0,S-triesters of phosphorodithioic acid which fall within the above general formula, many have been previously reported in the literature. J. H. Bartlett (US. Pat. No. 3,159,664) discloses, for instance, cyclic 0,0-2,Z-dimethyltrimethylene S-a-methylbenzyl phosphorodithioate and its method of preparation; and the compound bis(cyclic 0,0-2,Z-dimethyltrimethylene) dithiobis(phosphorothioate) has been reported by R. S. Edmundson in Tetrahedron, vol. 21, pp. 2379-2387, (1965). It should be understood, however, that these two compounds have not been previously described as accelerating agents within or without the temperature limits of the invention. Although synergistic combinations of thiazole accelerators and zinc phosphorodithioate 0,0-diesters are known (see US. Pat. No. 3,308,103 to Coran), it will be hereinafter shown that such compounds are inferior accelerating agents compared with the compounds of the invention at the elevated curing temperatures of the inventive technique.

A new type of adduct disclosed herein is the result of the addition of DTP and its homologues to a grouping. This is a new reaction previously unreported. This type of adduct is exemplified by cyclic 0,0-2,2- dimethyltrimethylene S-[a-(benzylidenehydrazino)- benzyl] phosphorodithioate whose preparation is described in Example 7 below.

PREPARATION The following examples illustrate the preparation of various adducts that are within the invention.

EXAMPLE 1 This example illustrates the preparation of cyclic 0,0-2,Z-dimethyltrimethylene S-a-methylbenzyl phosphorodithioate which is the Markovnikoff 1:1 mole addition product of cyclic 0,0-2,Z-dimethyltrimethylene phosphorodithioic acid and styrene.

10.4 g. (0.1 mole) of peroxide-free styrene was added dropwise during 5 minutes to a continuously stirred solution of 19.8 g. (0.1 mole) of cyclic 0,0-2,2- dimethyltrimethylene phosphorodithioic acid in 200 ml. of reagent benzene at room temperature. The mixture was then stirred and refluxed for 9 hours. Evaporation of the solvent gave a liquid which crystallized very slowly. Recrystallization from cyclohexane gave a solid having a melting point of 84-85.5C. The yield of recrystallized product was 9.5 g. (3l.5% of theory).

Analysis for C H O PS Cald. C, 51.64; H, 6.33; P, 10.24; S, 21.21. Found. C, 51.45; H, 6.28; P, 10.01; S, 20.34.

The preparation of this particular adduct has been reported in the literature (U.S. Pat. No. 3,159,664 to J. H. Bartlett).

EXAMPLE 2 This example illustrates the preparation of the anti- Markovnikoff 1:1 mole addition product of cyclic 0,0-2,Z-dimethyltrimethylene phosphorodithioic acid and styrene.

A mixture of 20.8 g. (0.2 mole) of commercial grade styrene, 39.6 g. (0.2 mole) of cyclic 0,0-2,2- dimethyltrimethylene phosphorodithioic acid in 100 ml. of reagent benzene and 0.697 g. (0.004 mole) of tertbutyl peroxypivalate (a 75% solution in mineral spirits) was stirred and heated at 45C for 20 minutes and then was heated to reflux. Refluxing and stirring were continued for 7 hours. A 2 ml. portion of the reaction solution was evaporated to dryness and the residue after recrystallization from Skellysolve melted at 67-7lC. A second recrystallization from Skellysolve raised the melting point to 72-75C. A third recrystallization from Skellysolve raised the melting point to 75.5-77C. A fourth recrystallization from Skellysolve raised the melting point to 7677.5C. A mixed melting point with cyclic 0.0-2,Z-dimethyltrimethylene phosphorodithioic acid was 5259.5C. The mixed melting point with a purified sample (melting point 84-85.5C) of the product of Example 1 (the Markovnikoff 1:1 adduct) was 57-62C.

Analysis for C H O PS Cald. C 51.64; H, 6.33; P, 10.24; M01. wt 302.4. Found. C, 51.63; H, 6.37; P, 10.36; M01. wt

303.0. These mixed melting points and the analyses indicate that the product was neither the recovered dithioic acid nor the product from Example 1, but was the anti- Markovnikoff 1:1 mole additionproduct, viz., cyclic 0,0-2,Z-dimethyltrimethylene S-phenethyl phosphorodithioate.

EXAMPLE 3 This example illustrates the preparation of cyclic 0,0-2,Z-dimethyltrimethylene S-[ 1,2,3a,4,7,7ahexahydro-4,7-methanoinden-2-yl] phosphorodithioate, which is the 1:1 mole adduct of dicyclopentadiene (3a,4,7,7a-tetrahydro 4,7-methanoindene) and cyclic 0,0-2,2-dim'ethyltrimethylene phosphorodithioic acid (DTP).

39.6 g. (0.2 mole) of cyclic 0,0-2,2- dimethyltrimethylene phosphorodithioic acid was dis solved at room temperature in 200 ml. of dry toluene contained in a 500 ml., 3-neck, round bottom flask equipped with a stirrer, thermometer, reflux condenser and dropping funnel. To the resultant solution, while stirring continuously, was added 25.4 g. (0.2 mole) of dicyclopentadiene through the dropping funnel during a period of 10 minutes. The ensuing exothermic reaction raised the temperature of the reaction mixture to about 52C. in 10 minutes, the solution remaining colorless. After 24 hours at room temperature, the solution was placed in a beaker on a warm steam bath. As the solvent (toluene) evaporated, a white solid crystallized from solution. After 24 hours, the mixture was filtered to remove the white, solid product which weighed 54.6 g. After recrystallization from Skellysolve and airdrying, the melting point of the product was 113l 16C. A second recrystallization from Skellysolve gave a product with a melting point of 113.5-1l5.5C.

Analysis for C 1-l O PS (1:1 mole adduct):

Cald. C, 54.52; H, 7.02; P, 9.37; S, 19.41. Found. C, 53.83; H, 6.82; P, 8.89; S, 18.08.

An infrared spectrum of the above 1:1 mole adduct showed the complete absence of absorption at 1610 cm", which is characteristic of the double bond between carbon atoms 2 and 3 in the following formula:

An absorption maximum was present, however, at 1575 cm, which is characteristic of the double bond between carbon atoms 5 and 6, indicating that the DTP had added across the double bond between carbon atoms 2 and 3.

EXAMPLE 4 9.2 g. (0.1 mole) norbornadiene was added dropwise during 67 minutes to a continuously stirred solution of 39.6 g. (0.2 mole) cyclic 0,0-2,2- dimethyltrimethylene phosphorodithioic acid in 150 ml. of reagent benzene at room temperature. An exothermic reaction caused the temperature of the mixture to rise to 585C. When the temperature had dropped to 40C., product began to crystallize from the reaction mixture. Filtration of the mixture gave 39.0 g. of product (79.9% of theory). The melting point (184l94C.) of the crude product was raised to l94195C. by recrystallization from hot cyclohexane.

Analysis for C,-,H O P S (1:2 mole adduct):

Cald. C, 41.79; H, 6.19; P, 12.68; mol. wt., 488.6. Found. C, 41.28; H, 5.89; P, 12.74; mol. wt., 459.0.

EXAMPLE 5 This example illustrates the preparation of cyclic 0,0-2,Z-dimethyltrimethylene S-l-methylheptyl phosphorodithioate, which is the adduct of l'octene and cyclic 0,0-2,Z-dimethyltrimethylene phosphorodithioic acid.

11.2 g. (0.1 mole) of l-octene was added to 19.8 g. (0.1 mole) of cyclic 0,0-2,Z-dimethyltrimethylene phosphorodithioic acid at room temperature. An exothermic reaction did not occur. After heating the reaction mixture at 100C. for 8 hours, it was placed under reduced pressure (25-35 mm.) at a temperature of 7585C. on a rotary evaporator for 2 hours. The residual, viscous liquid weighed 30.3 g. (98% of theory).

Analysis for C H O PS Cald. C, 50.29; H, 8.76; P, 9.97; S, 20.66. Found. C, 49.92; H, 8.64; P, 9.84; S, 20.0.

EXAMPLE 6 This example illustrates the preparation of cyclic 0,0-2,Z-dimethyltrimethylene S,S-[2,2'-( 1,3- pheny1ene)diisopropyl] phosphorodithioate, which is the adduct of 2 moles of cyclic 0,0-2,2- dimethyltrimethylene phosphorodithioic acid and one mole of m-diisopropenylbenzene.

15.8 g. (0.1 mole) of m-diisopropenylbenzene, which had been purified by passage through chromatographic alumina, was added dropwise while stirring for 6 minutes to a solution of 39.6 g. (0.2 mole) of cyclic 0,0-2,Z-dimethyltrimethylene phosphorodithioic acid in 150 ml. of reagent benzene at room temperature. A slightly exothermic reaction caused an elevation of 5C. in the temperature of the reaction mixture. After stirring for one hour, the mixture was heated to, and maintained at, 60-65C., with continuous stirring, for 5 hours. Evaporation of the solvent left a crystalline product, covered with a thin layer of clear viscous syrup. The melting point of the crude solid, after washing with Skellysolve, was lll.5-1l5C. Recrystallization from a 4:1 mixture of cyclohexane and benzene gave 24.3 g. of product (43.8% of theory for a 2:1 adduct). Another recrystallization from a 5:1 mixture of Skellysolve and chloroform gave a product melting at 109.5-116C.

Analysis for C H O P S (2:1 mole adduct):

Cald. C, 47.62; H, 6.54; P, 11.17; S, 23.12; mol. wt., 554.7. Found. C, 47.32; H, 6.32; P, 11.18; S, 25.60; mol. wt., 582.0.

EXAMPLE 7 This example illustrates the novel preparation of cyclic 0,0-2,2-dimethyltrimethylene S-[a-(benzylidenehydrazino)benzyl] phosphorodithioate, which is the adduct of 1 mole of cyclic 0,0-2,2- dimethyltrimethylene phosphorodithioic acid to 1 mole of l,2-di(benzylidene) hydrazine. 1,2-di(benzylidene)- hydrazine itself is the condensation product of 2 moles of benzaldehyde and lmole of hydrazine.

To a solution of 39.6 g. (0.2 mole) of cyclic 0,0-2,2- dimethyltrimethylene phosphorodithioic acid in 150 ml. of reagent benzene was added, dropwise, with continuous stirring over aperiod of 5 minutes at 25C., a solution of 20.8 g. (0.1 mole) of 1,2-di (benzylidene)- hydrazine. The resultant mild exothermic reaction caused the temperature of the mixture to rise 5C. and within 15 minutes a yellow precipitate began to form. Stirring was discontinued after a total of 2 /2 hours, after which the mixture was filtered to isolate the yellow product which had a melting point of 13l.5-l35.5C. Recrystallization of the yellow product from a mixture of 1 liter of cyclohexane and 0.5 liter of benzene gave 28.3 g. of product melting at 132-1 35C. A second recrystallization raised the melting point to 135-l36C.

Analysis for C H N O PS (1:1 mole adduct): Cald. C, 56.14; H, 5.70; P, 7.62; S, 15.78. Found. C, 54.81; H, 5.78; P, 7.77; S, 15.33.

The elemental analysis indicated that the product obtained was a 1:1 molar addition product of the phosphorodithioic acid and the azine. The yield of product before recrystallization was 37.3 g. or 91.9% of theory.

EXAMPLE 8 This example illustrates the preparation of cyclic 0,0-2,Z-dimethyltrimethylene S-(oxo)-ahydroxyphenethyl phosphorodithioate. This is the 1:1:1 mole adduct of cyclic 0,0 -2,2- dimethyltrimethylene phosphorodithioic acid, styrene and oxygen.

To a solution of 39.6 g. (0.2 mole) of cyclic 0,0-2,2- dimethyltrimethylene phosphorodithioic acid in 125 ml. of reagent benzene in a Parr oxygenator bottle was added 20.8 g. (0.2 mole) of styrene. The bottle was placed quickly into the oxygenator and 40 pounds of oxygen pressure from an oxygen cylinder was applied while shaking the reactants. Within 2 hours, a mild exothermic reaction occurred during the uptake of 0.129 moles of oxygen. The reaction mixture was cooled to room temperature. The solid product, weighing only 2.5 grams after drying, was filtered ,off. The reaction mixture-filtrate was diluted with ml. of toluene, washed with two 100 ml. portions of 8% aqueous sodium bicarbonate solution, one (1) 100 ml. portion of water, then freed of solventand dried under reduced pressure (2 mm. at 70C. for 2 hours). The weight of the very viscous, ambercolored, taffy-like residuewas 37 g. (553% of theory).

Analysis for C H O PS Cald. C, 46.69; H, 5.73; P, 9.26. Found. c, 48.41; H, 5.62; P, 9.02.

An infrared spectrum of the chemical, (C,5H O PS showed absorption maxima at: (l) 3450 cm (presence of OH group); (2) 685 cm (presence of P=S grouping); (3) 1050 cmand 990 cm" (presence of P--OC grouping).

The reaction 0.0-the previous example is not unique. Thus the addition of DTP according to the disclosure in the presence of oxygen under pressure results in the S(oxolahydroxyform of the resultant compound. For example. in the case of Example 5, 0.0-2.Z-dimethyltrimethyleneS-(oxol-Z-hydroxynoctyl phosphorodithioate; and in the case of Example 10. lauryl 3-[cyclic 0.0-2.2dimethyltrimethylene phosphorodithioyl(S-ox)l2-hydroxypropionate.

EXAMPLE 9 This example illustrates the preparation of bis (cyclic 0,0-2,2-dimethyltrimethylene) dithiobis(phosphorothioate).

To a solution of 39.6 g. (0.2 mole) of cyclic 0,0-2,2- dimethyltrimethylene phosphorodithioic acid in 200 ml. of absolute methanol was added a solution of 25.4 g. (0.2 atomic weight) of iodine in 200 ml. of absolute ethanol at 25C. in one portion with continuous stirring. The reaction mixture was stirred continuously for 48 hours, after which a solid product was isolated by filtration, washed with a small amount of absolute ethanol, and then air-dried. Recrystallization from ethanol solution yielded 9.1 grns. (23% of theory) of a white solid with a melting point of 135-l37C.

Analysis for C H O P S Cald. C, 30.45; H, 5.11; P, 15.70. Found. C, 30.77; H, 5.24; P, 15.02.

The preparation of this particular product has been reported in the literature (Tetrahedron, vol. 21, pp. 2379-2387, 1965).

EXAMPLE This example illustrates the preparation of lauryl 2- (cylic 0,0-2,Z-dimethyltrimethylene phosphorodithi oyl) propionate, which is the 1:1 mole adduct of cyclic 0,0-2,Z-dimethyltrimethylene phosphorodithioic acid to lauryl acrylate.

To a solution of 19.9 g. (0.1 mole) of cyclic 0,0-2,2- dimethyltrimethylene phosphorodithioic acid in 70 ml. of methylene chloride was added 24 g. (0.1 mole) of lauryl acrylate in small portions over a period of about one-half hour. The reaction mixture was then refluxed for 2% hours and then washed successively with 50 ml. of saturated, aqueous sodium bicarbonate solution and 100 ml. of distilled water. The washed solution was then treated with Darco (activated charcoal), filtered and evaporated. The residual liquid was placed under reduced pressure (3 mm.) for 5 hours at 90C. The weight of the clear viscous liquid was 36.2 g. (yield 82.4% of theory, calculated as the 1:1 mole adduct). An infrared spectrum showed the absence of the vinyl unsaturation characteristic of the lauryl acrylate.

Analysis for C H O PS Cald. c, 54.77; H, 8.96; P, 7.06. Found. C, 55.70; H, 8.85; P, 7.07.

The elemental analyses showed that the chemical was the 1:1 mole adduct as indicated above.

Use of the Triesters as Accelerators In the process of vulcanizing rubbers, it is desirable to accelerate the vulcanization rate so that the production efficiency of a given size vulcanization unit can be increased. One approach to this result has been to raise the vulcanization temperature, but the resulting vulcanizates have shown themselves to be of inferior quality in several respects. The present compounds, on the other hand, are very good co-accelerators of the sulfur vulcanization process at elevated temperatures (i.e., at least about 350 to 400F) when used in combination with such primary accelerators as the thiuram sulfides and disulfides, the dithiocarbamates and the thiazoles. It thus becomes possible to shorten the cure time very substantially. For example a 30 minute cure at 320F. can be shortened to just 5 minutes at 400F.

EXAMPLE 1 1 This example demonstrates the use of the chemicals of the invention. Normally they function as accelerators and generally can be used with any conventional accelerator, e.g., a thiazole, a dithiocarbamate, a thiuram monosulfide, a thiuram disulfide or a sulfenamide type accelerator.

Code Chemical Name A Tetramethylthiuram monosulfide B Zinc 0,0-bis(4-methyl-2-pentyl) phosphorodithioate C Cyclic 0,0-2,2-dimethyltrimethylene S-amethylbenzyl phosphorodithioate D Cyclic 0,0-2,Z-dimethyltrimethylene S-[ 1,2,

The compound formula (Base Formulation) used in this evaluation was:

Parts by Weight Royalene 302* 100.0 HAF black 50.0 Circosol ZXH 25.0 Zinc oxide 50 Stearic acid 1.0 Sulfur 1.5 Z-Mercaptobenzothiazole 0.5

An ethylene-propylene'dicyclopentadiene terpolymer (EPDM) having an iodine number of 10. an ethylene-propylene ratio of 60-40 and a Mooney viscosity (ML-4 at 212F.) of 90.

"A naphthenic-typc oil; specific gravity 0.9279. Saybol! viscosity at 210F. 61 seconds. Color ASTM. 2.5. Aniline point. 179F.

Two known prior art accelerators appear as compounds A and B. A is Monex (tetramethylthiuram monosulfide) and B is a zinc diester of phosphorodithioic acid [zinc 0,0-bis(4-methyl-2-pentyl) phosphorodithioate]. The particular zinc phosphorodithioate used for comparison purposes is one which in combination with MBT gives a synergistic effect when used to accelerate the sulfur vulcanization of ethylenepropylene terpolymers using a thiazole-type accelerator (U.S. Pat. No. 3,308,103 to Coran). Chemicals C to K are the nine chemicals whose preparation is given in the above examples 1, and 3-10, inclusive. Two different cures, viz., (l) a 30 minute cure at 320F., and (2) a 5 minute cure at 400F., were used. Stressstrain data, including Shore A hardness results, were obtained 16 mers of about 95 to 99 parts of isobutylene and correspondingly 5 to 1 parts of isoprene, the solution polyon test pieces which had been vulcanized in a press at the two different temperatures indicated.

Table l Stock 1 2 3 4 5 6 7 8 9 10 ll l2 l3** Base Formulation I83 183 I83 Hi3 I83 133 183 I83 183 I83 183 183 182.5 (MBT 0.5)

Chemical K 3.0 Property For Minute Cure at 32()F. Shore A 59 55 47 52 52 47 57 56 52 53 34 47 46 (l)Tcnsilc,psi 32H) 3350 840 1730 820 940 2300 3230 l 170 2880 145 I040 500 (2)El0ng., 7a 510 570 I070 900 1000 980 640 640 I000 690 l 140 950 1000 (3 )S-300,psi l [70 9 l 5 210 325 210 315 700 710 245 575 90 225 I30 Bloom* 2 l l l l l l l l i 1 Property For 5 Minute Cure at 400F. Shore A 56 49 5'. 53 55 Si 55 57 55 51 41 Tensile, psi 3220 1870 2760 2660 2620 2560 2850 2820 3I90 2100 I750 Elongation. 7! 620 790 780 720 750 790 610 750 590 510 810 S-300, psi 820 405 525 525 455 465 735 805 525 690 260 Bloom* 3 4 l l l l 2 Z 2 l 1 After one l week at room temperature: 1 none. 2 very slight: 3 moderate; 4 heavy (I) Tensile strength at break (2) Ultimate elongation (3] Modulus of elasticity at 30071. elongation Base formulation without (1.5 pt of MBT The results given in Table 1 show that the chemicals of the invention acting as co-accelerators give good high temperature (e.g. 400F.) sulfur cures; substan tially equivalent to the cures obtainable with prior art accelerators such as the thiuram sulfides and the Zinc diesters of phosphorodithioic acid. The comparison of the high temperature (400F.) cure with the standard temperature (320F.) cure shows incipient reversion in the Monex stock (A) and appreciable reversion of the zinc diester stock (B). Stocks C to J show that adequate physical properties were developed after only 5 minutes at 400F. with no evidence of reversion. It is obvious that satisfactory cures can be obtained at tempera tures between 320F. and 400F. and above by proper adjustment of the cure time. An outstanding characteristic of the chemicals of this invention is that unlike the prior art accelerators they produce vulcanizates with very little or no bloom, thereby making them especially useful in injection molding formulations.

The accelerators of the invention can be used to accelerate the sulfur vulcanization of both low and high unsaturation rubbers.

Examples of low unsaturation rubbers are: (l) the EPDM rubbers prepared by interpolymerizing a monomeric mixture containing ethylene, a higher alpha monoolefin containing 3-16 carbon atoms and a polyene having two or more carbon-to-carbon double bonds. The preferred polyenes include dicyclopentadiene, 1,4-hexadiene, 1,3-pentadiene, cyclooctadiene, cyclooctatetraene, tridecadiene, 5-methylene-2- merization being effected at low temperature in the presence of a Friedel-Crafts polymerization catalyst of the type of aluminum chloride or boron trifluoride.

Examples of high unsaturation rubbers include natural rubber, synthetic rubbers, and mixtures thereof. The synthetic rubbers may be the products of the polymerization of various monomers. Such synthetic rubbers are: (l) polymers of butadienes such as 1,3- butadiene, Z-methyl-l ,3-butadiene(isoprene), 2- chloro-l ,3-butadiene (chloroprene), 2,3-dimethyl-l ,3- butadiene piperylcne, 1(or 2)-phenyl-l,3-butadiene and copolymers of mixtures thereof; and (2) copolymers of mixtures of one or more of such 1,3-butadienes with up to 70% of such mixtures of one or more monoethylenic monomers which contain a group. Examples of such monoethylenic monomers include aryl olefins such as styrene, vinylnaphthalene, lx-methylstyrene, p-chlorostyrene, the a-methylenecarboxylic acids and their esters, nitriles, and amides, such as acrylic acid, methyl acrylate, methyl methacrylate, acrylonitrile, methacrylonitrile, methacrylamide; methyl vinyl ether; methyl vinyl ketone; vinylidene chloride; vinylpyridines such as 2-vinylpyridine, 2-methyl-5-vinylpyridine; vinylcarbazole. Commercial synthetic rubbers of this type, made by aqueous emulnorbomfine, e, sion polymerization with a peroxide catalyst, are SBR 5-a-propylidene-2-n0 0rn 0p 0py i n (copolymer of butadiene and styrene) and NBR (cono orn y n polymer of butadiene and acrylonitrile). Some of these 5-isobutylidene-Z-norbornene, 5-(2-methyl-2- butenyl)-2-norbornene, 5-(3-methyl-2- butenyl)n0rbornene and 5-(3,5-dimethyl-4-hexenyl)- 2-norbornene; (2) the butyl rubbers which are copolyrubbers may be prepared by the solution polymerization of: l )1,3-butadiene using as catalyst the reaction product=of aluminum trialkyl and titanium tetrachloride or (2) 2-methyl-1,3-butadiene(isoprene), using as catalyst the reaction product of aluminum trialkyl and titanium tetrachloride.

EXAMPLE 12 Results similar to those of example 11 are obtained when, isoprene (synthetic or natural), styrenebutadiene (SBR) and acrylonitrile-butadiene (NBR) rubbers are used in the inventive techniques.

The inventive accelerators are particularly useful in the production of vulcanized rubber articles reinforced with polyester (linear terephthalate polyester) fibers such as those described by Daniels in U.S. Pat. No. 3,051,212 and Chantry in U.S. Pat. No. 3,216,187. These rubber articles include pneumatic tires, V-belts, flat belts, Timing belts (toothed power or synchronizing belts), footwear, coated fabrics, rubberizedfabric containers, etc. When these articles are made using a rubber vulcanizing system with the so-called delayed action accelerators such as the thiurams or the sulfenamides, it has been found that these accelerators exert a deleterious effect on the polyester fiber reinforcement. This deleterious effect is accentuated when the article is subjected to elevated temperatures in service, such elevated temperatures arising from environmental heat and/or internal heat generated by repeated flexure as in the case of a pneumatic tire or a belt. Apparently these accelerators during the cure and/or in service form a basic environment which accelerates hydrolytic and/or chain scission of the polyester molecules which in turn causes degradation in the physical properties of the composite article.

The inventive accelerators are uniquely suited as coaccelerators in sulfur vulcanizin g systems using thiuram or sulfenamide accelerators because at the elevated curing temperatures of about 400F. they generate acidic products which can counteract the basic products of the thiuram or sulfenamide accelerators. This counteraction by the inventive accelerators results in a less basic environment which in turn greatly reduces the degradation of the polyester fiber reinforcement.

Typical sulfur-containing vulcanizing agents which are examplary of the vulcanizing agents to be used in the inventive technique are:

vulcanizing Agent parts/100 parts rubber Sulfur 1.0 2.5

Tuex (tetramethylthiuram 2.0 4.0

disulflde) Ethyl Tuex (tetraethylthiuram 2.5 4.5

disulfide) Vultac (alkyl phenol disulfides) 5.0 12.0

Sulfasan R (4,4-dithiodimor- 4.0 6.0

pholine) It should be understood that the particular sulfurcontaining vulcanizing agent selected and the amount thereof used for vulcanization is not critical to the practice of the inventive technique; the type and quantity of vulcanizing agent used need only be that as would effect vulcanization under ordinary prior art conditions.

Typical prior art accelerators with which the inventive accelerators can be used are, in addition to M BT and MBTS:

Sodium 2-mercaptobenzothiazole Zinc Z-mercaptobenzothiazole 2,2-dithiobisbenzothiazole 2-(morpholinothio)-benzothiazole 2-benzothiazolyl l-hexamethyleniminecarbodithioate 2-benzothiazo1yl thiolbenzoate l ,3-bis( 2-benzothiazolylmercaptomethyl)urea 2-(2,4-dinitrophenylthio)benzothiazole S-(2-benzothiazolyl)N-diethyl dithiocarbamate N-cyclohexylbenzothiazole-Z-sulfenamide N-tert-butylbenzothiazole-2-sulfenamide In general, the weight ratio of the inventive accelerator to the prior art accelerator is from 1:1 to 5:1, with about 2:1 preferred. The rubber compositions which can be cured with the inventive accelerators can contain the usual added additional ingredients, such as sulfur, pigments, antioxidants and/or antiozonants, fillers, extenders, etc. Curing temperatures can range from about 400F. up to the highest permissible temperature depending upon such well-understood factors as the time of cure, and the type of rubber, prior art accelerator, activator, etc., used.

Of course, it is readily apparent to those skilled in the art, that there are variations of the invention which can be made without departing from its scope and spirit, and all such variations which basically rely on the teachings disclosed herein are considered to be within the scope of the foregoing description and appended claims.

Having thus described our invention, what we claim and desire to protect by Letters Patent is:

1. A compound having the following formula:

1 R CH wherein R and R are C, to C alkyl groups which can be the same or different; and R is a-hydroxyphenethyl.

3. The compound cyclic 0,0-2,2- dimethyltrimethylene S-(oxo)-a-hydroxyphenethyl phosphorodithioate. 

1. A COMPOUND HAVING THE FOLLOWING FORMULA:
 2. A compound having the following formula:
 3. The compound cyclic O,O-2,2-dimethyltrimethylene S-(oxo)-Alpha -hydroxyphenethyl phosphorodithioate. 